GSR tranny Final drive question
 

Long story short... did a drop on the freeway playing with some bikes. after pull i hear a transmission whine under load in all gears... I am suspecting missing tooth/teeth on final drive. Using new Mfactory LSD and it worked great for the last year.

boosted
677hp
GSR tranny, LS 5th


Question is, I am looking into upgrading the tranny slightly. I am trying to put together what would make most sense.


Basically what I have is :
1st: 3.23:1
2nd: 1.90:1
3rd: 1.36:1
4th: 1.03:1
5th: 0.714:1
Final: 4.40:1

And now the top speeds in each gear, hit at 8100RPM. You'll get a bit more if you shift at the rev-limiter. (NOTE redline is about 9200 now)

1st: 38mph
2nd: 65mph
3rd: 92mph
4th: 122mph ---->>>> this is the problem I am running short of top speed and losing time I run out of 4th and have to shift to fifth.
5th: Drag limited somewhere under 140mph



I am thinking upgrade final drive, liberty cuff and speedfactory SCHA

I am seeing trap speeds at about 120 on street tires 235/50/15 at the track at a constant 12.2 (spinning for a 60ft of 2.2) at 9psi
Also running out of 4th gear before the end of the track and have to shift into 5th about 50 ft before the 1/4mile mark. I mean I could just ride it in banging of the rev limiter but I chose not to lol

However I also have 24" slicks but its hard for me to make it to the track all the time, so I mostly street the car.


Looking specifically at the street tire setup, would it be wise to go with a 4.266 Final drive over a 4.05 final drive?

Looking specifically at the slick size, would the idea of having a 4.266 final drive be better or worse?

Or should I be looking elsewhere , maybe a higher final drive than the 4.4 that is currently in the transmission?

Please chime in, I am new to transmission setups, I usually just kept the stock gsr..

My goal is to get a better 1/4mile time and faster trap speed. I think this is acheivable with a final drive changeout for more top speed?

Re: GSR tranny Final drive question
 

If you're hitting 122 at 8,100 and can wind it out to 9,200, just wind it out. Changing to a longer FD will make the car slower and running cuff isn't practical for the street. If you are set on changing it you need to decide what tires you're going to run, then you can pick a ratio.